It may have been an attempt to prevent some from returning after the war; their property in most cases was taken when they disappeared (either by force or flight), and their return would have presented problems to a lot of impacted countries.
On the flip side, I assume few wanted to return to their European birthplaces.
Did Stalin have a Jewish wife and stepdaughter?
https://www.jweekly.com/2007/09/27/did-stalin-have-a-jewish-wife-and-stepdaughter/